Method and device for uphill casting, comprising a chill or core stackings with an open pouring gate

ABSTRACT

A method for uphill/low-pressure casting, especially of light metal alloys, with a casting table having a flow-through opening, with a casting furnace lying below the casting table with a riser pipe forming an upwardly open mouth opening, with a mould having a base plate which has a downwardly open pouring-in opening; the mouth opening is positioned against the flow-through opening in a sealing fashion from below, the mould is brought with its pouring-in opening over the flow-through opening, melt is conveyed from the casting furnace via the riser pipe into the mould until it is filled, the mould is displaced horizontally on the casting furnace with open melt-filled communication between the casting furnace and the mould until the pouring-in opening is closed by the casting table below and the flow-through opening is closed by the base plate above, the melt is allowed to drop in the riser pipe as far as below the mouth opening.

[0001] The invention relates to a method and an apparatus for uphillcasting, especially for the casting of light metal alloys. Compared withgravity casting, uphill casting has the substantial advantage of asmooth controlled casting process. By this means the entrance of airbubbles and oxidation skin which is associated with any turbulence ofthe melt during casting is avoided. When using core packages as moulds,the separation and entrainment of moulding material in the gate and inthe runner can be avoided which otherwise leads to a deterioration inthe quality of the castings.

[0002] A disadvantage with uphill casting is that in general it isnecessary to wait for the solidification process of up to 15 minutesduration before the mould just filled can be removed and the next mouldcan be brought over the casting furnace. In order to rectify thisdisadvantage, it has already been proposed that moulds should be closeddirectly after the low-pressure casting in the pouring-in opening andremoved immediately from the riser pipe.

[0003] DE 198 21 419 A1 and DE 198 07 623 A1 disclose methods of thespecified type in which boxless mould bodies (core packages) or mouldingboxes each having a downwardly open pouring-in opening are pushed overthe mouth of the riser pipe of a casting furnace which lies beneath aconveyer for these mould bodies (core packages) or moulding boxes. Afterthe uphill casting, in each case a closure at the upper end of the riserpipe is first closed before the mould body (core package) or themoulding box is transported further and replaced by a following one.

[0004] The object of the invention is to improve a method and anapparatus of said type in order to increase the reliability. Thesolution for this according to a first approach consists in a method foruphill/low-pressure casting, especially of light metal alloys, with acasting table having a flow-through opening, with a casting furnacelying below the casting table with a riser pipe forming an upwardly openmouth opening, with a mould having a base plate which has a downwardlyopen pouring-in opening; the mouth opening is positioned against theflow-through opening in a sealing fashion from below, the mould isbrought with its pouring-in opening over the flow-through opening, meltis conveyed from the casting furnace via the riser pipe into the moulduntil it is filled, the mould is displaced horizontally on the castingfurnace with open melt-filled communication between the casting furnaceand the mould until the pouring-in opening is closed by the castingtable below and the flow-through opening is closed by the base plateabove, and the melt is allowed to drop in the riser pipe as far as belowthe mouth opening.

[0005] According to a second approach a method for uphill/low-pressurecasting, especially of light metal alloys, is proposed with a castingtable having a flow-through opening, with a casting furnace lying belowthe casting table with a riser pipe forming an upwardly open mouthopening, with a mould having a base plate which has a downwardly openpouring-in opening, the mouth opening is positioned against theflow-through opening in a sealing fashion from below, the mould isbrought with its pouring-in opening over the flow-through opening, meltis conveyed from the casting furnace via the riser pipe into the moulduntil it is filled, the mould is left in this position until the castinghas solidified, the melt is allowed to drop in the riser pipe as far asbelow the mouth opening, the mould is displaced horizontally on thecasting table with its flow-through opening emptied of melt, until thepouring-in opening is closed by the casting table below and the mouthopening is closed by the base plate above.

[0006] An apparatus suitable for implementing these methods comprises acasting table with a flow-through opening, a casting furnace lying belowthe casting table with a riser pipe, forming an upwardly open mouthopening, a mould with a base plate having a downwardly open pouring-inopening; the mouth opening is positioned against the flow-throughopening in a sealing fashion from below, the mould is positioned withits pouring-in opening against the flow-through opening from above,means for horizontal displacement of the mould on the casting table andmeans for simultaneously maintaining a positive pre-pressure of themould base plate towards the casting table.

[0007] With the means specified hereby it is possible to completelydispense with a slide valve closure, rather in each case forcasting/mould filling, the sprue of the mould and the flow-throughopening in the casting table or the mouth opening of the riser pipe arebrought together so that they connect and melt is conveyed into themould until it is filled. Then, according to the first attempt, directlyafter the casting/mould filling, the mould with still-liquid melt in thedownwardly open sprue is displaced with respect to the flow-throughopening of the casting table or the mouth of the riser pipe on thecasting table such that the previously uniform melt column in the riserpipe and in the sprue is directly and exclusively sheared by thedisplacement of the sprue of the mould with respect to the flow-throughopening in the casting table or the mouth opening of the riser pipe.Acting as closure means here are the upper side of the casting tablewhich can be reinforced with an inserted ceramic plate or rail, and theunderside of the base plate of the mould which lie flat one on top ofthe other. According to the second attempt, however, after casting/mouldfilling, solidification of the casting is first awaited until only thesprue still contains liquid melt, which is then allowed to drop in theriser pipe by lowering the pressure before the emptied sprue isdisplaced with respect to the flow-through opening of the casting tableor the mouth of the riser pipe on the casting table such that next mouldcan be transferred.

[0008] Whereas in the first method an active pressure application fromabove is suitable, in the second method the pressure is produced via themelt in the riser pipe.

[0009] In order that floating of the mould is avoided during casting,said surfaces can be pressed onto one another with contact pressure.This is possible by means of horizontal rails or sets of rollers securedelastically to the casting table, which act on fixed horizontal edges orrails of the mould to press the mould on the casting table duringdisplacement or by means of horizontal rails or sets of rollers arrangedelastically on the mould which interact with horizontal edges or railsarranged fixed on the casting table to press the mould on the castingtable. Suitable pairs of materials for these surfaces are to be selectedaccording to the type of casting metal.

[0010] The moulds can be conveyed into the casting position in variousways, wherein either the mould is in each case placed from above on thecasting table so that the flow-through opening or the mouth opening isin open communication with the pouring-in opening or whereinalternatively, the mould is in each case transferred horizontally overthe casting table so that the flow-through opening or the mouth openingis in open communication with the pouring-in opening.

[0011] After casting and displacement, the mould can be held in aposition in which the casting table under the pouring-in opening of themould is cooled. In addition to this, the mould with the pouring-inopening can be moved during displacement over the cooled section of thecasting table. By means of these two measures rapid solidification ofthe melt is in the sprue achieved after which the mould can be liftedfrom the casting table or the corresponding conveying means withsolidification not yet completed.

[0012] For rapidly solidifying small castings it is favourable toarrange two moulds in a tandem arrangement on the base plate with twopouring-in openings. For larger, more slowly solidifying castings it ispossible to provide a carousel arrangement in which a plurality ofmoulds are mounted on a common base plate with a ring of pouring-inopenings.

[0013] Further advantageous embodiments of the method and suitableapparatus are deduced from the dependent claims to which reference ishereby made.

[0014] Insofar as uphill casting/low-pressure casting according to theinvention is discussed heretofor, this initially relates to methods andapparatus wherein a controllable gas pressure is applied to the meltlevel in the sealed casting furnace, which makes the melt in the riserpipe rise or fall. Also included however are other methods and apparatuswhich can controllably convey the melt in the riser pipe, e.g. magneticpumping arrangements at the lower end of the riser pipe in the castingfurnace.

[0015] Preferred embodiments of the invention are explained in thefollowing with reference to the drawings wherein:

[0016] FIGS. 1 to 8 show an apparatus according to the invention with acasting table, casting furnace and two moulds, with the individualphases:

[0017]FIG. 1 Build-up of a pre-pressure in the casting furnace; mould 1in casting position;

[0018] mould 2 is opened;

[0019]FIG. 2 Casting of mould 1; mould 2 is closed;

[0020]FIG. 3 Mould 2 in casting position; mould 1 in solidificationposition;

[0021]FIG. 4 Casting of mould 2; mould 1 is opened;

[0022]FIG. 5 Casting of mould 2; demoulding of mould 1;

[0023]FIG. 6 Mould 1 in casting position; mould 2 in solidificationposition;

[0024]FIG. 7 Casting of mould 1; mould 2 is opened;

[0025]FIG. 8 Casting of mould 1; demoulding of mould 2;

[0026]FIG. 9A casting installation according to the invention with aplurality of moulds

[0027] a) viewed from the top

[0028] b) viewed from the side;

[0029]FIG. 10 shows a casting installation according to the inventionwith a smelting furnace, two casting stations and four casting furnaces.

[0030] FIGS. 1 to 8 are first described jointly insofar as the detailsagree. A horizontal casting table 11 has a flow-through opening 12 whichis lined with an outer lining 13 and an inner lining 14. Below thecasting table 11 there is a casting furnace 21 having a riser pipe 22which is inserted in the casting furnace in a sealing fashion and at thebottom is immersed in the melt 23 contained therein and at the top has amouth opening 24. An arrow 25 indicates that compressed air can beapplied to the casting furnace 21 so that a melt column 26 rises in theriser pipe 22. On the casting table are located two moulds designated bythe numbers “1” and “2” which have a common base plate 30. This baseplate 30 has pouring-in openings 31, 32 which can be brought to coverthe flow-through opening 12 alternatively by transverse displacement ofthe base plate 30. The pouring-in openings 31, 32 are each provided withlinings 33, 34. The moulds 1, 2 mounted on the base plate 30 each haveholders 35, 36, 37, 38 with adjusting cylinders 39, 40, 41, 42 which acton mould halves 43, 44, 45, 46. Midway between the mould halves there isa central mandrel 47, 48, respectively, whose suspension is not shown indetail. Together with the closed mould halves this mandrel 47, 48respectively forms a hollow cylinder with slightly conical inner shapeand external ribbing. The casting to be produced using the moulds 1, 2shown can especially be a light-metal cylinder liner for combustionengines. Changes in volume and shape of the casting duringsolidification are neglected in all representations.

[0031] In the embodiment shown the riser pipe 22 adjoins the castingtable 11 at the bottom in the area of the flow-through opening 12 in asealing fashion. For this purpose the casting furnace 21 can beadjustable in height from below towards the casting table 11 with theriser pipe 22 suspended elastically in the casting furnace 21. Therespective pouring-in opening 31, 32 in the base plate 30 in each caselies on the upper outlet of the flow-through opening 12 in a sealingfashion.

[0032] Lowering of the casting furnace is especially advantageous toexchange an empty casting furnace for a filled casting furnace.

[0033] In FIG. 1 a pre-pressure is built up in the casting furnace whichmakes the melt column 26 rise as far as slightly above the mouth opening24. The mould 1 is allocated to the casting furnace 21 by displacing thebase plate 30 to the right into a first casting position. The mould 1 isclosed, as indicated by arrows and ready for casting. The mould 2 isopened, as indicated by arrows and demoulded.

[0034] In FIG. 2 the pre-pressure in the casting furnace 21 is increasedso that the melt column 26 has risen and the mould 1 is completelyfilled. The casting process as such is already ended here. The mould 2is now shown closed, as indicated by the arrows.

[0035] In FIG. 3 the base plate 30 is displaced to the left into asecond casting position wherein the melt column in the mould 1 has beensheared between the casting table 11 and the base plate 30 and afinished casting has formed in mould 1. Mould 2 is allocated to thecasting furnace 21 by displacing the base plate 30 to the left into asecond casting position and is in the closed position ready for casting.Immediately after shearing at the mould 1, the melt column 26 isinitially made to drop again in the riser pipe 22 as far as slightlyabove the mouth opening 24. In FIG. 4 mould 1 is opened as indicated byarrows, wherein the finished casting is held still on the centralmandrel 47. In mould 2 the melt column has risen as a result of apressure increase in the casting furnace so that the mould is completelyfilled. The actual casting process has already ended here.

[0036] In FIG. 5 the mould 1 is re-closed wherein the finished casting49 is completely demoulded. Mould 2 is shown as in FIG. 4 during thecasting process.

[0037] In FIG. 6 the base plate 30 has been displaced to the right againinto the first casting position so that the mould 1 is again allocatedto the casting furnace 21. The melt column in mould 2 has thereby beensheared so that a finished casting can be identified in the mould. Mould2 is still closed to wait for the solidification process. Mould 1 isprepared for the next casting process wherein the melt column 26 endsslightly above the mouth opening 24 in the riser pipe 22.

[0038] In FIG. 7 mould 2 is opened as shown by arrows wherein a finishedcasting still sits on the central pin 48. In mould 1 the melt column 26has risen as a result of increasing the pre-pressure in the castingfurnace 21 and is thus filled, so that the actual casting process iscompleted here.

[0039] In FIG. 8 the casting 50 is removed from mould 2 and the mould isre-closed for the next casting process. Mould 1 is in the same positionas in FIG. 7 and by displacing the mould with the base plate the meltcolumn 26 is sheared in the next moment between the base plate 30 andthe casting table 11.

[0040]FIG. 9 shows a casting table 51 with a flow-through opening 52 andcooling positions 53, 54 indicated by arrows. Below the casting table isa casting furnace 61 with a riser pipe 62 filled with melt. The mouthopening 64 of the riser pipe 62 adjoins the flow-through opening 52 frombelow. Three individual moulds 71, 72, 73 are placed on the castingtable 51. The mould 71 has its sprue 74 over the casting furnace 61 andis directly engaged in the casting process. The mould 72 has alreadybeen displaced left with respect to the flow-through opening 52 whereinthe melt column has been sheared and is located in a position where thesprue 75, 76 in the mould 72, 73 lies above a cooling region 53 of thecasting table. The mould 73 is displaced further and is located in aposition in which the sprue 75,76 in the mould 72, 73 lies over acooling region 53, 54 of the casting table wherein solidification hastaken place in the sprue 76. From here the mould can be displacedfurther or lifted directly from the casting table. Arrows 77, 78indicate the effect of a pre-pressure which prevents escape of the meltduring filling of the mould. An arrow 79 indicates the effect of ahigher active pressure for feeding.

[0041]FIG. 10 shows a top view of an apparatus according to theinvention wherein a casting table 91 is only constructed as a narrowpath. The casting table here has two casting stations 92, 93 withflow-through openings 94, 95 and two solidification stations 96, 97.Moulds 101, 102 can each be placed on the casting stations from abovefor casting wherein, after casting, they can be displaced and then takeon the positions of the moulds 103, 104 shown here during soldification.Casting furnaces ND1, ND2, ND3, ND4 can be brought into the vicinity ofa melting furnace 111 and from there can be moved into a holdingposition before the casting stations 92, 93, into a casting position andinto a holding position behind the casting stations 92, 93 so that emptycasting furnaces can each be refilled at the melting furnace 111 andafter a casting furnace has been emptied, a filled casting furnace canimmediately be refilled from a waiting position into the castingposition under the casting table. At least one of the casting stations92, 93 of the casting table should always be ready for casting so thatthere is no interruption of production during changing a castingfurnace. In the normal case, the two casting stations can also be run inparallel to increase the production rate.

1. A method for uphill/low-pressure casting, especially of light metalalloys, with a casting table having a flow-through opening, with acasting furnace lying below the casting table with a riser pipe formingan upwardly open mouth opening, with a mould having a base plate whichhas a downwardly open pouring-in opening; the mouth opening ispositioned against the flow-through opening in a sealing fashion frombelow, the mould is brought with its pouring-in opening over theflow-through opening, the melt is conveyed from the casting furnace viathe riser pipe into the mould until it is filled, the mould is displacedhorizontally on the casting table with open melt-filled communicationbetween the casting furnace and the mould until the pouring-in openingis closed by the casting table below and the flow-through opening isclosed by the base plate above, the melt is allowed to drop in the riserpipe as far as below the mouth opening.
 2. The method foruphill/low-pressure casting, especially of light metal alloys, with acasting table having a flow-through opening, with a casting furnacelying below the casting table with a riser pipe forming an upwardly openmouth opening, with a mould having a base plate which has a downwardlyopen pouring-in opening, the mouth opening is positioned against theflow-through opening in a sealing fashion from below, the mould isbrought with its pouring-in opening over the flow-through opening, meltis conveyed from the casting furnace via the riser pipe into the moulduntil it is filled, the mould is left in this position until the castinghas solidified, the melt is allowed to drop in the riser pipe as far asbelow the mouth opening, the mould is displaced horizontally on thecasting table with its flow-through opening emptied of melt, until thepouring-in opening is closed by the casting table below and the mouthopening is closed by the base plate above.
 3. The method according toone of claims 1 and 2, wherein the mould is in each case placed on thecasting table from above so that the flow-through opening or the mouthopening is in open communication with the pouring-in opening.
 4. Themethod according to one of claims 1 and 2, wherein the mould is in eachcase transferred horizontally over the casting table so that theflow-through opening or the mouth opening is in open communication withthe pouring-in opening.
 5. The method according to one of claims 1 to 4,wherein during the uphill casting and the displacement of the mould, themould is held under pre-pressure against the casting table or the riserpipe.
 6. The method according to one of claims 1 to 5, wherein duringthe uphill casting and the displacement of the mould, the riser pipe isheld under pre-pressure against the casting table or the base plate ofthe mould.
 7. The method according to one of claims 1 or 3 to 6, whereinafter the displacement of the mould, the mould is held in a position inwhich the casting table is cooled under the pouring-in opening.
 8. Themethod according to one of claims 1 or 3 to 7, wherein duringdisplacement of the mould, the mould together with the pouring-inopening is guided over a section of the casting table which is cooled.9. The method according to one of claims 1 to 8, wherein two moulds arealternately mounted on a base plate with two pouring-in openings, castand demoulded, wherein the base plate alternately with the pouring-inopenings is displaced over the flow-through opening or onto the mouthopening.
 10. The method according to one of claims 1 to 8, wherein aplurality of moulds are sequentially mounted on a base plate with a ringof pouring-in openings, cast and demoulded, wherein the base plate isturned in a carousel fashion with the pouring-in openings over theflow-through opening or the mouth opening.
 11. An apparatus for uphillcasting/low-pressure casting, especially for casting light metal alloys,with a casting table with a flow-through opening, with a casting furnacelying below the casting table with a riser pipe, forming an upwardlyopen mouth opening, with a mould with a base plate having a downwardlyopen pouring-in opening; the mouth opening is positioned against theflow-through opening in a sealing fashion from below, the mould ispositioned with its pouring-in opening against the flow-through openingfrom above, characterised by means for horizontal displacement of themould on the casting table and means for simultaneously maintaining apositive pre-pressure of the mould base plate towards the casting table.12. The apparatus according to claim 11, characterised in that the mouldhas coolant above a non-cooled sprue region.
 13. The apparatus accordingto one of claims 11 or 12, characterised by horizontal rails or sets ofrollers secured elastically to the casting table which act on fixedhorizontal edges or rails of the mould to press the mould on the castingtable during displacement.
 14. The apparatus according to one of claims11 or 12, characterised by horizontal rails or sets of rollers arrangedelastically on the mould which interact with horizontal edges or railsarranged securely on the casting table to press the mould on the castingtable.
 15. The apparatus according to one of claims 11 to 14,characterised by means for pressing the riser pipe on the casting tableor the mould.
 16. The apparatus according to claim 15, characterised bya riser pipe suspended elastically in the casting furnace and heightadjustment means for the casting furnace.
 17. The apparatus according toone of claims 11 to 16, characterised by two moulds placed on a commonbase plate with two pouring-in openings, especially permanent moulds, aswell as means of displacement for alternating displacement of the baseplate.
 18. The apparatus according to one of claims 11 to 16,characterised by a plurality of moulds placed on a common base platewith a ring of pouring-in openings, especially permanent moulds, as wellas rotating drive means for rotating drive of the base plate.